double result = Math.log( value );

System.out.println("logarithm: " + result );

sqrt() Method

Here is sample output from the (unmodified) program:

C:\chap11>java SquareRoot
Enter a double: 3
square root   : 1.7320508075688772

It is OK to enter a number without a decimal point (as the "3" above) for floating point IO. Java converts it to the correct type.

Here is some of the documentation for the method sqrt():

static double sqrt(double a) 
Returns the correctly rounded positive square root of a double value. 

This was copied from the Java documentation you probably have in your Java Development Kit subdirectory. It also can be found at: java.sun.com